Phosphorus for Plants: Source of Energy

         For the plant – a source of energy.
          

      Phosphorus plays an exceptionally important role in energy exchange processes in plant organisms.

     The physiological significance of phosphorus is determined by its inclusion in a number of organic compounds – nucleic acids (DNA and RNA), nucleotides (ATP, NAD, NADP), nucleoproteins, vitamins, and many others, which play a central role in metabolism. Phospholipids are components of biological membranes, with the presence of phosphate in their structure ensuring hydrophilicity, while the rest of the molecule is lipophilic. Many vitamins and their derivatives containing phosphorus act as coenzymes and participate directly in catalytic reactions that accelerate the course of essential metabolic processes (photosynthesis, respiration, etc.). Phosphorus is found in the organic compound phytic acid (Ca–Mg salt of inositol phosphoric acid), which is the main storage form of phosphorus in the plant. Phytic acid is particularly abundant in seeds (up to 1–2% of dry weight).
    The energy of sunlight during photosynthesis and the energy released during the oxidation of previously synthesized organic compounds during respiration is accumulated in plants in the form of energy from phosphate bonds in so-called high-energy compounds, the most important of which is adenosine triphosphate (ATP). The energy accumulated in ATP during photosynthetic and oxidative phosphorylation is used for all vital processes of growth and development of the plant, for the absorption of nutrients from the soil, for the synthesis of organic compounds, and their transport. A deficiency of phosphorus disrupts energy and matter exchange in plants.

      Phosphorus enters the root system and functions in plants in the form of oxidized compounds, mainly residues of orthophosphoric acid (H₂PO₄^–, HPO₄^2–, PO₄^3–). In all transformations within the plant organism, phosphorus retains its oxidation state, with all transformations reducing to either the addition or transfer of the phosphate residue (phosphorylation and transphosphorylation).

    Phosphorylation is the addition of a phosphate residue to an organic compound, forming an ester bond, for example, the interaction of phosphoric acid with a carbonyl, carboxyl, or alcohol group. Protein phosphorylation is carried out by protein kinases and regulates the course of metabolic reactions in the organism, including protein and RNA synthesis, enzyme activity regulation, and underlies the functioning of signaling pathways. Other compounds can also be phosphorylated. For example, during the phosphorylation of sugars, sugar phosphates – esters of sugars and phosphoric acid – are formed. These compounds are more labile and reactive than free sugars, playing a significant role in respiration, in the mutual transformations of carbohydrates, and in their synthesis.
    Transphosphorylation is the process by which a phosphate residue, included in one organic compound, is transferred to another organic compound. A number of biologically important phosphorus compounds contain several phosphate residues. Phosphorus is characterized by its ability to form bonds with high energy potential (high-energy bonds). Such bonds are unstable, facilitating their exchange and allowing energy to be used for biochemical and physiological processes themselves. An important compound containing high-energy phosphorus bonds is ATP. When phosphoric acid enters the living cells of the plant root, it quickly becomes incorporated into nucleotides, forming AMP and ADP. Subsequently, ATP is formed during substrate-level and oxidative phosphorylation (anaerobic and aerobic phases of respiration).

    The phosphorus content in plants is about 0.2% based on dry weight.

    A particularly pronounced deficiency of phosphorus affects the formation of reproductive organs in all plants. Its insufficiency slows down development and delays seed maturation, causing a decrease in yield and deterioration of its quality. Plants with insufficient phosphorus significantly slow down growth, and their leaves acquire (first at the edges, and then over the entire surface) a gray-green, purple, or red-violet color. In cereal grains, phosphorus deficiency reduces tillering and the formation of fruiting stems. Signs of phosphorus starvation usually manifest at the early stages of plant development when they have a poorly developed root system and are unable to absorb poorly soluble phosphates from the soil.

   Enhanced phosphorus supply to plants accelerates their development and allows for an earlier harvest, while also improving its quality.

    Medicinal plants containing phosphorus:
    • species of wormwood Artemisia L., Asteraceae (herb, content – 1.2–1.3%);
    • Gmelin’s Hedysarum Hedysarum gmelinii Ledeb., Fabaceae (herb, content – 1.03%);
    • feather grass Stipa pennata L., Poaceae (herb, content – 0.88%);
    • tuberous Phlomis Phlomis tuberosa L., Lamiaceae (tubers, herb, content – 0.85%);
    • creeping thyme Thymus serpyllum L., Lamiaceae (herb, content – 0.67%);
    • smooth brome Bromopsis inermis (Leys). Holub, Poaceae (herb, content – 0.65%);
    • shrubby cinquefoil Pentaphylloides fruticosa (L.) O. Schwarz., Rosaceae (herb, content – 0.13–0.5%);
    • red clover Trifolium pratense L., Fabaceae (leaves, inflorescences);
    • rowan Sorbus aucuparia L., Rosaceae (fruits – 1% *);
    • species of hawthorn Crataegus L., Rosaceae (fruits – 1% *).